Cartridge tape drives are extensively used for archival backup of computerized user digital information, and are increasingly used as an information library tool, particularly on the so-called "world-wide web" or "internet". The information is typically written onto the tape as a linear track (or tracks) of magnetic flux transitions as the tape is drawn or "streamed" past a write head element. Typically, blocks of tape are successively streamed to the tape as it moves at high speed from a "beginning of tape" or "BOT" indicator, to an "end-of-tape" or "EOT" indicator. Alternatively, the digital information may be written in transverse tracks as the tape is drawn past a helical scan, rotating head array of the type employed in video cassette recording technology.
Since magnetic recording tape is a very thin, flexible plastic strip coated on one side with a magnetic storage material, it is susceptible to damage. The tape may become stretched or warped, and its edges may become damaged or frayed. Accordingly, tape cartridges have been developed in order to minimize physical damage to the tape during loading and unloading of the tape onto the tape drive. There are two basic types of tape cartridge: the self-contained feed and take-up reel cartridge, and the single, feed reel cartridge which includes a coupling or buckling mechanism at a leader end of the tape supply coiled on the single cartridge.
In order to achieve commercial success, it has been necessary for the industry to standardize tape cartridges and tape within the cartridges, so that cartridges following a particular standard may be received and used by tape drives designed to handle the standard cartridge design. Standardization has imposed a second and even more severe design restraint, and that is that newer tape cartridge designs should be backward-compatible with older tape drives (and newer tape drives should likewise be backward-compatible with older tape cartridges), in order to maintain the agreed-to cartridge standards. The present invention provides an improvement to a standardized cartridge design for a single-reel tape cartridge presently marketed by the assignee of this application under the DLT.TM. Compactape.TM. brand. This cartridge is standardized e.g. by American National Standards Institute standard ANSI X3.197-1991 standard entitled "Unrecorded Magnetic Tape and Cartridge for Information Interchange--1/2 inch (12.65 mm), Serial Serpentine, 22-Track, 6 667 ftpi (262 ftpmm) and 48-Track, 10 000 ftpi (394 ftpmm)". This industry standard cartridge specification is incorporated by reference herein as relevant background material.
The standardized cartridge 10 (shown diagrammatically in FIG. 1 and in greater structural detail in FIGS. 2 and 3) is a two-part, generally rectangular box structure containing a single feed reel 16 of tape with five rigid walls and at least a portion of a sixth wall having a door or shutter 34 which opens as the cartridge 10 is inserted into a compatible tape drive in order to enable tape drive access to a coupling end of a tape supply coiled on the reel 16. The cartridge 10 includes e.g. two defined openings 36 and 38 leading to two internal reel locks 30 and 32. The reel locks 30 and 32 are located to act on a diameter of the reel 16 and the locks prevent the feed reel from rotating and the tape pancake from unraveling during cartridge handling outside of the standard tape drive. A tape leader includes a buckling mechanism, and the cartridge 10 typically includes features to restrain the buckling mechanism at a defined position adjacent the opening.
A cartridge-handling portion 20 of the standard tape drive is shown functionally in FIG. 1. The compatible tape drive for the standardized cartridge 10 has a base casting (not shown) to which a molded-plastic cartridge receiver 50 is secured. As viewed from a front opening, the receiver 50 is adapted to receive a standard single reel tape cartridge 10. The receiver 50 is a generally U-shaped channel structure having a left side 52, a right side 54 and a top 56, and defines openings at front and back. A metal plate floor 58 has a spindle opening and is attached to the channel structure to form a box. A molded plastic drive cover (not shown in FIG. 1) attaches to the receiver and to a front wall of the base casting. The receiver 50 includes a front opening for receiving the cartridge, and provides journals for a rotatable handle mechanism 66 (shown diagrammatically in FIG. 1).
The handle mechanism 66 rotates two levers, a first one of which (not shown in FIG. 1) has a first finger which enters a standardized locating hole in the bottom of the cartridge when the handle is pushed flush with the front cover after the cartridge 10 is inserted. The other lever 66 has a second finger 68 which is also brought into engagement with the cartridge 10. While this second finger 68 may have a secondary locating function, a primary function of the second finger 68 is to release one of the feed reel locks within the cartridge 10.
Suspended between the two levers is a plate 70 with a slight rotational degree of freedom, and with a central opening. When the handle is in the open position, admitting the tape cartridge, the levers are pushed downwardly away from the receiver, and the plate engages a spring-loaded clutch mechanism on the feed reel motor fixed to the drive base. This action pushes the tape spindle assembly downwardly and out of the path of the cartridge 10. Conversely, when the handle mechanism is returned to its engaged, flush-against-the-front-panel position, the clutch plate 70 releases the spindle, and the plate 70 elevates the spindle into a nominal operating engagement with the single reel within the cartridge 10.
An annular toothed ring 72 of the spindle engages a complementary annular toothed plate of the feed reel within the cartridge. A feed reel motor 74 is directly coupled to rotate the drive ring 72 and thereby rotate the reel within the standard cartridge 10. A spring mechanism within the cartridge 10 provides a bias force to the feed reel, and this force is overcome when the spindle ring engages the feed reel toothed plate. Beveling of the ring and plate facilitate centering of the reel on the spindle when the spindle is engaged. One example of a tape cartridge including a spring-biased feed reel in accordance with the published standard is described in U.S. Pat. No. 5,027,249 to Johnson et al., entitled: "Tape Cartridge Bearing", the disclosure thereof being incorporated herein by reference.
A fixed cartridge door actuation structure 76 on the left sidewall 52 of the receiver 50 cooperates with a door opening structure 78 of the cartridge 10, so that as the cartridge 10 is pushed into the receiver 50 engagement of the fixed structure 76 with the cartridge door release structure 78 automatically opens the door 34 of the cartridge to expose the tape buckling mechanism. On the right sidewall of the receiver a solenoid-actuated, hinged locking dog 64 extends into a third standardized opening 42 defined in the cartridge 10. This third opening 42 comprises a notch in the right sidewall of the cartridge 10. Rotation of the locking dog 64 by the solenoid unlatches the handle mechanism 66 and allows the handle to be opened. Otherwise, once the cartridge 10 is loaded into the receiver 50 the cartridge locking dog 64 prevents the cartridge from coming out. The locking dog structure also carries a second micro switch which senses a user-activated write protect mechanism 44 which selectively opens and blocks a write protect window 46 formed in the sidewall of the cartridge adjacent the notch 42.
When the cartridge 10 is properly loaded into the receiver 50, the cartridge's right sidewall and opening 38 become precisely registered with reference datum planes of the receiver 50 and thereby with the feed reel spindle ring 72 of the tape drive. At the same time, the cartridge tape-protection features including the door and the two diametrically opposed reel locks become respectively opened and disengaged, thereby enabling the tape drive mechanism to buckle to the tape buckling mechanism and to draw the tape along a defined tape path within the drive, with tape tension controlled by the feed reel motor 74 as well as by a counter-torque applied by a take up reel motor to a take-up reel within the tape drive.
In the present example shown in FIGS. 2 and 3, the standardized cartridge 10 includes a two-part molded plastic housing including a top cover 12, and a bottom cover 14. The tape reel 16 is wound with a spool 18 of magnetic recording tape 18. The reel 16 may include only a top flange as shown in FIG. 3, or it may preferably include a top and a bottom flange. The flanges may provide a tape-wedging function be in accordance with the teachings of commonly assigned U.S. Pat. No. 5,474,253, entitled: "Wedged Reels in Streaming Tape Drives and Tape Cartridges", the disclosure thereof being incorporated herein by reference.
A center of rotation of the reel 16 is biased toward the bottom cover 14 and away from the top cover 12 by a coiled spring 21. A spring-loaded hub structure 22 engages a ball bearing assembly 24, the outer races of which engage a cylindrical flange of the plastic reel 16. Reel engagement teeth formed as an annulus 26 about the center of rotation of the reel 16 enable the reel to be rotated by the spindle ring 72 and spindle motor 74, once the cartridge 10 is loaded into the receiver mechanism 20 of a compatible tape drive 50. One reel flange of the reel 16 has outer peripheral teeth 28 which are engaged by toothed pawls of reel locks 30 and 32. The reel locks 30 and 32 are spring biased toward the reel periphery to lock the reel in place.
The cartridge 10 includes the hinged door 34 which is automatically opened by the structural features 76 of the compatible receiver 20 as the cartridge 10 is received therein, so that a buckle 35 of a tape leader of the tape 18 becomes exposed and thereupon may be engaged by an automatic tape buckling mechanism for bucking a drive leader to the tape leader. A suitable two-part tape buckling mechanism is shown in commonly assigned U.S. Pat. No. 4,572,460 to Hertrich, entitled: "Means for Pulling Tape From a Reel". Engagement and disengagement of the two parts of the tape buckling mechanism within the standard drive is more particularly described in commonly assigned, copending U.S. patent application Ser. No. 08/666,854 filed on Jun. 19, 1996, and entitled: "Improved Tape Buckling Mechanism for Single Reel Cartridge Tape Recording", now U.S. Pat. No. 5,769,346, the disclosure thereof being incorporated herein by reference.
The industry-standard cartridge 10 is provided with several cartridge-locating features, including an end wall slot 36, two bottom wall slots 38 and 40, and a side recess 42. In addition, a write-protect mechanism 44 alternatively blocks and exposes a window 46 in the sidewall of the cartridge 10. End wall slot 36 provides access for releasing reel lock 30, while bottom wall slot 38 provides access for releasing reel lock 32.
With reference again to FIG. 1, the receiver mechanism 52 includes a reference side wall 54, top wall 56, bottom wall 58 and end wall 60. These surfaces serve as datum planes to locate the cartridge 10 within the receiver 50. The end wall 60 includes a fixed pin 62 which passes through end wall slot 36 and engages reel lock 30, thereby rotating it away from the toothed periphery 28 of reel 16. A spring-biased latching pawl 64 includes a toothed portion which enters the side recess 42 and thereby locks the cartridge 10 inside of the receiver. A rotational latch mechanism 66 includes a locating/release pin 68 which passes through end wall opening 38 to release the other reel lock 32. A registration pin (not shown) may be provided as part of the rotational latch mechanism for entering the other end wall opening 40 and further register the cartridge 10 within the receiver. Accurate registration is needed to ensure that the toothed engagement ring 26 will precisely center with, and be engaged by, a reel motor drive mechanism. In addition, accurate registration is also needed to ensure accurate mating between a take up leader nose and a supply leader hoop.
The described combination of standard tape cartridge 10 and standard tape drive 50 has worked well for many years, with one principal drawback that the "form factor" of the cartridge and the "form factor" of the tape drive have remained substantially invariant over the years. This combination has occupied either a full-height 5.25 inch drive bay or a half-height 5.25 inch drive bay of a computer. A recent trend has been to provide disk and tape drives in smaller "form factors". One prevalent form factor is the so-called 3.5 inch form factor, because many computer designers specify, and computer cabinets provide, 3.5 inch drive bays, rather than 5.25 inch drive bays.
The need to reduce tape drive form factor to serve physically smaller computing systems has been recognized. A similar trend has been experienced in the hard (non-removable) disk drive art, and in the optical disk art. For removable media drives, particularly those performing backup or archival data storage service, backward compatibility becomes a critical and limiting condition. Cartridge adapters have been proposed for adapting smaller media units for compatible handling by larger media drives.
One example is the ubiquitous VHS-C cartridge used in many hand held video cassette recorder products and the surprisingly complex VHS-C adapter unit which adapts the small VHS tape video camera cartridge to a standard-size VHS cartridge and VCR playback unit. In at least one form, the VHS-C cartridge adapter carries a dry cell and includes a battery-operated DC motor for loading and unloading the VHS-C cartridge within the adapter before it is able to be handled within a conventional set-top VHS video recording/playback device. While this cartridge adapter is widely used, it is also quite complicated, and relatively expensive.
Another example is provided in U.S. Pat. No. 5,402,954, entitled "Videotape Adapter for Use With A Cartridge", and U.S. Pat. No. 5,082,196, entitled: "Video Cartridge Adapter Interlock System". A further example of a cartridge adapter is described in U.S. Pat. No. 5,331,627, entitled: "Cartridge Adapter". The '627 patent describes an optical disk cartridge adapter for holding a 90 mm optical disk cartridge within a drive adapted to receive a 130 mm optical disk cartridge. A "pseudo-spindle" was provided to interconnect the drive spindle with the smaller disk spindle opening. In addition, a rotating permanent magnet was provided directly above a shutter opening of the smaller cartridge in order to present a bias field to enable writing of the 90 mm magneto-optical media in the smaller cartridge.
Each of these prior, vastly different, cartridge approaches suggests that providing a workable miniaturized cartridge and a compatible cartridge adapter can be a daunting engineering challenge. This challenge is largely dependent upon the particular characteristics and requirements of the standard cartridge to which the miniaturized cartridge of different design will be adapted for handling by a drive or cartridge loader designed to handle the larger-sized standard cartridge. As a standard cartridge becomes imbued with many unique features for locating, reel-locking and releasing, write protecting, etc., the difficulty in adapting the defined standard for compatible use with a smaller form-factor cartridge becomes manifestly complex.
Thus, a hitherto unsolved need has remained for a form-factor-reduced single reel tape mini-cartridge and cartridge adapter enabling a standard form-factor tape drive to handle and access tape stored in the mini-cartridge.